Nonindigenous Ants Associated with Geothermal and Human Disturbance in Hawai'i Volcanoes National Park!

JAMES K. WETfERER2

ABSTRACT: Although the Hawaiian Islands lack indigenous ants, more than 40 exotic species have become established there, primarily in lowland areas, where they have been implicated in the extermination of much of the endemic Hawaiian fauna. In June to August 1994, I surveyed ants in the K.I1auea Caldera region (elevation 1090-1240 m) of Hawai'i Volcanoes National Park to evaluate the current range and potential impact of ants in this protected montane ecosystem. Ants were common in areas disturbed by geothermal or human activity, but rare in undisturbed forest. A total of 15 ant species was collected, including 10 "lowland" ant species that are generally restricted to elevations below 900 m in Hawai'i. Pheidole megacephala and Anoplolepis longipes, major pest species in lowland Hawai'i, occurred in very high densities in and around the geothermal area near the park headquarters. Paratrechina bourbonica and Cardiocondyla venustula, two cold-tolerant species, were the most common ants in a second geothermal area, the Puhimau hot spot, and in areas disturbed by human activity, including roadsides. Linepithema humile, a major pest species in drier highland areas, occurred only in and around park buildings. The geothermal areas and park buildings appear to serve as warm "habitat islands" that allow Ph. megacephala, A. longipes, and other lowland ants to extend their ranges to higher elevations. Colonization of geothermal areas by lowland ant species, such as Ph. megacephala and A. longipes, poses a threat to endemic Hawaiian species in those areas. Colonization of roadsides and other disturbed areas by more cold-tolerant ants, such as P. bourbonica, C. venustula, and L. humile, poses a more general threat to endemic Hawaiian species found at higher elevations.

THE HAWAIIAN ISLANDS have perhaps 10,000 less endemic fauna (Holldobler and Wilson endemic species of insects, including such 1990, Gillespie and Reimer 1993). Loss of unique forms as predaceous inchworms, in species that serve key functions in the natural tertidal crickets, and damselflies with terres community (e.g., important prey species, pol trial larvae (Howarth et al. 1988, Wilson linators, seed dispersers, scavengers, decom 1992). Like many other remote Polynesian posers) may have cascading effects leading to islands, however, the Hawaiian Islands lack severe disruptions of natural nutrient cycling an indigenous ant fauna (Wilson and Taylor and the subsequent loss of additional native 1967). When ants invade such islands, they plant and animal species (Howarth 1985). can have devastating effects on the native More than 40 species of exotic ants have ecosystems, preying on the relatively defense- become established in the Hawaiian Islands, primarily in lowland areas (Reimer 1994). Most of these species probably arrived ac companyirrg--human-traffic--to--Honolulu;-a 1 Financial support was provided by the U.S. National lowland port of entry on the island of O'ahu Biological Service, Wheaton College, and Columbia University. Manuscript accepted 3 March 1997. (Reimer 1994), where they had to survive 2 Center for Environmental Research and Conserva under lowland tropical conditions before tion, Columbia University, New York, New York 10027. spreading to other locales. This may explain 40 Ants in Hawai'i Volcanoes National Park-WIITTERER 41

why relatively few ant species have invaded passerine birds often depend heavily on feed the cooler highland areas of the Hawaiian ing insects to their nestlings. Such competi Islands (Reimer 1994). In the study reported tive exclusion may be, in part, responsible for here, I surveyed the KTIauea Caldera region the disappearance of most native Hawaiian of Hawai'i Volcanoes National Park on the forest birds from the lowlands, even in areas island of Hawai'i to evaluate the current where the forest has remained relatively in range and potential impact of exotic ants in tact (Banko and Banko 1976, Scott et al. that protected higWand habitat. 1986). Three ant species are currently recognized Linepithema humile, an important pest ant as major pests in the Hawaiian Islands: Phei of subtropical and temperate regions (Hol dole megacephala (Fabricius) (the bigheaded way 1995) was first found in Hawai'i at ant) and Anoplolepis longipes (Jerdon) (the an army base near Honolulu (Zimmerman longlegged ant) in lowland areas, and Line 1941), but quickly spread to other locales pithema humile (Mayr) (the Argentine ant, (Wilson and Taylor 1967). This species is now formerly Iridomyrmex humilis) in higWand considered the primary ant pest of higher areas (Reimer 1994). Pheidole megacephala elevations (above 900 m) in the Hawaiian was the first of these three to become estab Islands (Cole et al. 1992, Reimer 1994). Cole lished in Hawai'i. By 1880, it was one of et al. (1992) documented the extreme de the most common insects in the Hawaiian structive power of L. humile in the higWands Islands (Wilson and Taylor 1967). Anoplole of Maui. They found drastic reductions in pis longipes and Linepithema humile arrived the populations of native invertebrate species later; they were first collected in Hawai'i in directly attributable to the presence of L. 1952 and 1940, respectively (Wilson and humile. Linepithema humile is also a threat Taylor 1967). All three major pest species are to native vertebrate populations. Newell and highly aggressive and territorial, resulting in Barber (1913) described how L. humile at mutually exclusive territories (Fluker and tacks birds: "the workers swarm over young Beardsley 1970). chicks in such numbers as to cause their Pest ants in the lowlands of Hawaiian death.... nests of many birds are frequented islands have been implicated in the extermi by the ants in the same way, and the number nation of much endemic fauna (Reimer et al. ofyoung birds destroyed in this manner must 1990, Reimer 1994). Zimmerman (1948) re be considerable." ported that the "voracious immigrant ant," Several previous studies surveyed ants in Ph. megacephala, eliminates most endemic Hawai'i Volcanoes National Park (HVNP). insects throughout its range. Similarly, Hardy Huddleston and Fluker (1968) surveyed four (1979) implicated A. longipes in the loss of sites in HVNP and found four species ofants, most of the insect fauna at a lowland site including none of the three major pest species on the island of Maui. Native Hawaiian spi mentioned above (see Table 1). Later, Gagne ders have been exterminated in areas invaded (1979) sampled the canopies of trees at nine by Ph. megacephala and A. longipes, replaced sites along an elevational transect in HVNP by nonindigenous spiders (Gillespie and from 15 to 2400 m elevation and found three Reimer 1993). On the island of Niuafo'ou in ant species: two species at low elevations Tonga, A. longipes kills the hatchlings of the (Plagiolepis alluaudi Forel and Ph. mega endemic incubator bird (Megapodius pritch cephala) and one species at higher elevations ardii), first attacking the birds' eyes (Swaney (L. humile). Medeiros et al. (1986) sampled 1994). Anoplolepis longipes is also known to 15 sites in HVNP from sea level to 2000 m prey upon newborn pigs, dogs, cats, rabbits, elevation, including four building sites in the ··rats,andehiekens-tHaines--et- al.--l994j,Ants· Itilauea-Galdera-area.-'Fhey-found--a-total--of also may have an important indirect impact six species, including all three major pest on native vertebrate populations by elimi species (see Table 1). In addition, Medeiros et nating key invertebrate prey species (Banko al. (1986) reported two other species collected and Banko 1976). In particular, breeding by C. Davis (see Table 1). Finally, from 1988 42 PACIFIC SCIENCE, Volume 52, January 1998 to 1991, Clive Jorgensen and his associates 100-m intervals along transects, usually by surveyed for ants at 144 sites within HVNP, the side of a trail or road. At each station from sea level to 3000 m elevation (Jorgensen I laid out approximately 2 g of tuna near the et aI., unpubl. data). They found a total of 19 base of each of three trees or plants, spaced species of ants, bringing to 20 the total num 1.5-2.5 m apart along the transect. I then re ber of ant species reported from HVNP (see visited each station after 1-3 hr and collected Table 1). ants attracted to the baits. Fellers and Fellers This study was motivated by my observa (1982) used a similar baiting technique in tions ofextremely high densities of Ph. mega their survey of L. humile at high-elevation cephala and A. longipes throughout the geo sites on Maui. All surveys were conducted thermal area at the northern edge of KTIauea during daylight hours. Caldera (1200-1220 m elevation), near park As a measure of the density of ants at bait headquarters. The only previously published stations, I estimated the number of ants records of these lowland ant species at such visiting a station in a 5-min interval. "Low" high elevation were made by Medeiros et was defined as 10 or fewer ants, "medium" as al. (1986) at two sites located a short distance 10 to 100 ants, and "high" as more than 100 west ofthe geothermal area: one collection of ants. At low-density sites, ants often located Ph. megacephala at KTIauea Military Camp only one of the three baits. At high-density (1220 m elevation) and one collection of a sites, ants generally located all baits within single specimen of A. longipes at a nearby 5 min, and all baits were covered with several campground (1190 m elevation). My obser hundred ants within 15 min. vations suggested a recent large-scale inva Bait station sites were divided into five sion of lowland ants into this region. categories defined as follows. (1) "HQ geothermal" (n = 45, 1200-1220 m elevation): trails and roads through the geothermal area near the park headquarters, MATERIALS AND METHODS from the eastern edge of Sulfur Banks to the Between 21 June and 20 August 1994, I western edge of Steaming Bluff. The vegeta surveyed ants in the K.11auea Caldera region tion in this area is primarily grass, herbs, (19 0 25' N, 155 0 15' W; elevation 1090-1240 ferns, and stunted '6hi'a trees (Metrosideros m, annual rainfall -2.3 m) of Hawai'i Vol- polymorpha). Hundreds of tourists visit this canoes National Park (HVNP). KTIauea area daily. Caldera, at the summit of KTIauea Volcano, (2) "Puhimau hot spot" (n = 35, 1090 is located on the southeastern flank of the 1100 m elevation): permanent transects much larger Mauna Loa Volcano (summit marked with metal stakes through the Puhi elevation 4169 m). mau hot spot area, extended west to the 1974 I surveyed along marked transects, trails, lava flow and east to Chain of Craters Road. and roads and around park buildings, con- I also included the 300-m dirt road into the centrating efforts in two geothermal areas: hot spot area and 400 m along Chain of the Steaming Bluff-Sulfur Banks area near Craters Road adjacent to the hot spot area the park headquarters at the northern edge of (between the road into the hot spot area and K.11auea Caldera, and the Puhimau hot spot, the turnoff to Puhimau Crater). There is little 5 km to the south, near Puhimau Crater. The vegetation through most of this area because hot soil conditions in these areas prevent the of the high temperature of the soil. Few tour growth of trees and other plants with deep ists visit this area. root systems (see Glime and Iwatsuki 1994). (3) "Roadside" (n = 12, 1100-1120 m r-alsosurveyeo-tne1fre-as--surrounllin-g--the- - elevation:;-n-= l-;-l-ElO m-e1evationj:-€hain of Steaming Bluff-Sulfur Banks area, as well as Craters Road between Crater Rim Trail and along the trails and roads through primarily the turnoff for Puhimau Crater (10 in forest forested areas between the two geothermal and two in lava fields from the 1974 lava areas. flow), plus one site described below under I set out a total of 211 bait stations at "Forest." Ants in Hawai'i Volcanoes National Park-WETTERER 43

(4) "HQ periphery" (n = 63, 1160-1230 m (Table 1). All 15 species have been pre elevation): trails and roads through the area viously reported from other parts of Hawai'i immediately surrounding the Steaming Bluff (Huddleston and Fluker 1968) and have wide Sulfur Banks geothermal areas, from the cen distributions in the Pacific and elsewhere ter of the Kt1auea Military Camp to the west, (Wilson and Taylor 1967). Crater Rim Drive to the north, to the closed Ten of these species are considered to be part of Crater Rim Drive between Volcano "lowland" species in Hawai'i, usually re House and the start of Crater Rim Trail to stricted to elevations below 900 m (Reimer the east. (The drop-off into Knauea Caldera 1994). The other five species appear to be borders to the south.) Vegetation in these more "cold-tolerant" species and commonly areas ranges from mowed lawns of Kt1auea extend their ranges above 900 m elevation. I Military Camp and the park headquarters to included Pheidole megacephala and Anoplo closed-canopy forest on the trails between lepis longipes as lowland species, because the Steaming Bluff and the park headquarters. only previously published records of these These areas are disturbed by human activity ants above 900 m are from the same area as to differing degrees. this study. (5) "Forest" (n = 55, 1120-1200 m eleva tion): "undisturbed" closed-canopy forest, Ants at Bait Stations along Crater Rim Trail, between the end of the closed section of Crater Rim Drive and I found ants at 123 of the 211 (58%) bait Chain of Craters Road. The site where the station sites (Table 2). The density and spe trail crosses Crater Rim Drive at the Thur cies diversity of ants varied dramatically ston Lava Tube, I classified as "Roadside." among different parts of the study area Numerous tourists walk these trails each (Table 2). Ants were common only in areas day. disturbed by human or geothermal activity. In addition, I surveyed six building sites in Ants occurred at 87 of 93 (94%) highly dis the Knauea Caldera area, using baits and turbed geothermal and roadside sites. Ants asking park employees the location of any were at highest densities in the HQ geother ants they had seen. The six main areas I mal area, Where I found several hundred ants surveyed in this way were as follows: (1) Re at all 45 bait sites. Ants were more diverse, search Center buildings (1180 m elevation); but generally at lower densities, in the Puhi (2) Namakani Paio campground cabins and mau hot spot. Ants were common along cooking shelter (1190 m elevation); (3) roads, but not diverse (three species). In the Kt1auea Military Camp buildings (1220 m HQ periphery area ants occurred at 33 of 63 elevation); (4) Jagger Museum and Hawai (52%) sites. In closed-canopy forest within ian Volcano Observatory (1240 m elevation); the HQ periphery (about half the sites), ants (5) Park headquarters buildings: KUauea were generally absent. In other "undisturbed" Visitor's Center, Volcano House Hotel, and closed-canopy forest away from the disturbed Volcano Art Center (1210 m elevation); (6) areas, ants occurred at only 3 of 55 (5%) Volcano Golf Course restaurant and club sites. house (1240 m elevation). Pheidole megacephala and Anoplolepis Voucher ant specimens from this study longipes, major pest species otherwise largely have been deposited in the Museum of Com confined to lowland areas in Hawai'i, oc parative Zoology, Harvard University. curred only in the HQ geothermal area and the nearby HQ peripheral area. These two species were present in extremely high den sities~ in theH~-ge-otn-e1ih1IJ area ana- OCCl.F RESULTS pied mutually exclusive territories. Pheidole megacephala occupied the eastern part of the Summary ofAnt Species geothermal area (e.g., Sulfur Banks), whereas I collected a total of 15 different ant spe A. longipes occupied the western part (e.g., cies in the Kt1auea Caldera region of HVNP Steaming Bluff). I found lower densities of TABLE 1

ANT SPECIES COLLECTED IN HAWAI'I VOLCANOES NATIONAL PARK IN DIFFERENT STUDIES

STUDIES" "ELEVATION SPECIES H&F G M+ D J+ W LIMIT" (m)

"Lowland" species Anoplolepis longipes X 31 28 1,200 Pheidole megacephala XX 37 26 1,200 Cardiocondyla nuda 6 10 <900 Tapinoma melanocephalum 12 9 <900 Tetramorium bicarinatum X 3 5 <900 Monomorium monomorium 5 3 <900 Paratrechina longicornis 3 1 <900 Cardiocondyla emeryi X 4 1 <900 Monomorium pharaonis X 1 <900 Pheidole fervens 1 1 <900 Technomyrmex albipes X 3 <900 Plagiolepis alluaudi XX 11 1,000 Hypoponera sinensis I' <900 Camponotus variegatus 2 500 "Cold-tolerant" species Paratrechina bourbonica X X 37 44 1,200 Cardiocondyla venustula 46 29 1,900 Linepithema humile XX 7 9 2,800 Hypoponera punctatissima 1 7 1,200 Hypoponera opaciceps X X 2 I 2,700 Paratrechina vaga 64' , 1,200

"H&F, Huddleston and Fluker (1968); G, Gagne (1979); M+, Medeiros et al. (1986); D, C. Davis (in Medeiros et al. 1986; J+, Jorgensen et al. (unpubl. data); W, this study. "Lowland" and "cold-tolerant" defined in text; "elevation limit" from Reimer (1994). For Jorgensen et al. (unpubl. data) and this study, I list the total number of separate collection sites for each species. In this study, this includes bait stations along transects, surveys of building sites, and tbree observed introductions. • See text.

TABLE 2

CoLLECTION FREQUENCY OF ANT SPECIES AT THE 211 BAIT STATIONS AROUND KILAUEA CALDERA (SEE TEXT FOR DESCRIPTIONS) (TOTAL NUMBER OF COLLEGnONS ADD Up TO MORE THAN THE NUMBER OF SITES WITH ANTS BECAUSE MORE THAN ONE ANT SPECIES OCCURRED AT MANY SITES)

HQ PUHlMAU HQ SPECIES GEOTHERMAL HOT SPOT ROADSIDE PERIPHERY FOREST

"Lowland" species Anoplolepis longipes 24 1 Pheidole megacephala 20 5 Cardiocondyla nuda 7 2 Tapinoma melanocephalum 8 1 Tetramorium bicarinatum 1 4 Monomorium monomorium 1 1 Cardiocondyla emeryi 1 "Cold-tolerant" species Paratrechina bourbonica 2 10 10 19 2 _C@'dil2-cond)ifg venustulll 15 1 13 Linepithema humile :3 Hypoponera punctatissima 4 2 Hypoponera opaciceps

Sites with ants 45/45 31/35 11/13 33/63 3/55 Ants in Hawai'i Volcanoes National Park-WETTERER 45

Ph. megacephala at five bait sites in the HQ "undisturbed forest" sites, one of which was periphery, all within 150 m of the HQ geo more than 600 m from any disturbed area. thermal area: one on Crater Rim Drive north of the thermal area and four on the service Ants at Building Sites road east ofSulfur Banks. I found A. longipes at one bait site in the HQ periphery, at the I found ants, representing a total of seven start of the closed section of Crater Rim different species, in and around five of the six Drive east of Volcano House. building sites that I surveyed in the Kilauea Paratrechina bourbonica (Forel), a cold Caldera area (Table 3). The buildings around tolerant species, was the most widespread ant the Volcano Golf Course were completely species in this study (Tables 1 and 2). Within free of ants, possibly due to the use of pesti the HQ geothermal area, P. bourbonica at cides. high density cooccupied one site with A. The most widespread species at the build longipes at low density and was sole occupant ing sites were L. humile and A. longipes. I of another site. Paratrechina bourbonica was collected L. humile in or around five build common in the HQ periphery and around ings at three building sites and A. longipes in the Puhimau hot spot. Along roadsides, P. or around three buildings at two building bourbonica was the only common species, sites. I collected five other species at one and it occurred at two sites in "undisturbed building site each. Two species, P. bourbon forest," both within 200 m of a road. ica and Ph. megacephala, were also common Cardiocondyla venustula Wheeler (= Car at bait stations. The other three species, diocondyla "a" in Huddleston and Fluker however, I collected only at building sites. [1968] and Huddleston et al. [1968]: S. Cover I found large numbers of Pheidole fervens and N. Reimer, pers. comm.), another cold Smith by the back door of the Volcano Art tolerant species, was also common, but with Center and Paratrechina longicornis (La a more limited distribution than P. bour treille) in the cooking shelter at the Nama bonica (Table 2). Although C. venustula was kani Paio campground. Finally, I collected common in the HQ periphery and the Puhi Monomorium pharaonis (L.) (as well as Ph. mau hot spot, this species was absent from the HQ geothermal area and forest sites, and TABLE 3 was collected only once at a roadside site. I collected Linepithema humile (formerly SUMMARY OF ANT SPECIES FOUND AT EACH BUILDING Iridomyrmex humilis), a major pest species SITE, INCLUDING NUMBER OF DIFFERENT BUILDINGS WHERE I COLLECTED A SPECIES in drier highland areas, at only three bait station sites. These three sites were all within SITES" 150 m of park buildings: two on the Kilauea Military Camp and one near the park resi SPECIES RC NP KMC 1M HQ dential area. I also collected seven other ant species at "Lowland" species Anoplolepis longipes * 2 the bait stations, five lowland species [Car Pheidole megacephala * diocondyla nuda (Mayr), Tapinoma melano Paratrechina longicomis cephalum (Fabricius), Tetramorium bicarina Pheidole fervens tum (Nylander) (= T guineese [Bolton 1977]), Monomorium pharaonis Cardiocondyla emeryi * Monomorium monomorium Bolton (= M. "Cold-tolerant" species minutum Mayr [Bolton 1987]), and Cardio Paratrechina bourbonica I * * condyla emeryi Forel] and two cold-tolerant Linepithema humile 2* * 2* 2 species IH-ypoponera punctatissima-ERegeF) aRC, Research Center; NP, Namakani Paio campground; and Hypoponera opaciceps (Mayr)]. The five KMC, Kilauea Military Camp; JM, Jagger Museum and lowland species and H. opaciceps were re Hawaiian Volcano Observatory; and HQ, Volcano House Hotel, stricted almost entirely to the HQ periphery KJ1auea Visitor's Center, and Volcano Art Center. I found no ants in the buildings around Volcano Golf Course. The first and the Puhimau hot spot. H. punctatissima, four sites were also surveyed by Medeiros et al. (1986). " col however, also occurred in low densities at two lected by Medeiros et al. (1986). 46 PACIFIC SCIENCE, Volume 52, January 1998

megacephala) from material delivered to the cases more aggressive ants may have ex Research Center as described below. cluded other species from the tuna bait. It is possible that some of the specimens P. bourbonica P. New Introductions ofAnts to Hawai'i identified as are actually vaga, Volcanoes National Park because there are no satisfactory traits for distinguishing the workers of these two On three occasions during the course of species (Wilson and Taylor 1967). In fact, this study, I witnessed ants being imported Trager (1984) examined some of Wilson and into HVNP through human activity. On 22 Taylor's (1967) Polynesian and Melanesian June, a computer monitor was delivered to "vaga" material and found that it contained the Research Center from Texas by express "some workers ofbourbonica as well as those mail. Inside the cardboard walls of the box of at least two other distinct species, differing were several hundred M. pharaonis. On 13 in vestiture and proportions, and only one (or August, I found a few dozen L. humile living perhaps none) of which can be true vaga." inside a car belonging to a researcher who commuted to the Research Center from her home outside the park. On 17 August, a park DISCUSSION visitor found several hundred Ph. mega cephala inside a bag of bagels purchased Distribution and Spread ofAnts in Hawai'i from a supermarket in Hilo, near sea level. Volcanoes National Park All three of these ant species are common "tramps" that typically spread through col Although a diversity of ants occur in the ony budding (groups of workers accompany KIlauea Caldera region of Hawai'i Volca ing inseminated queens), increasing the pos noes National Park, they are common only sibility of successful colonization (H6lldobler in areas disturbed by human and geothermal and Wilson 1990). activity. This supports the observation that exotic species in general tend to be more successful at invading disturbed habitats Ants Not Found in This Study (Elton 1958, Orians 1986). Despite high den There are several ant species previously sities of ants in disturbed areas and along collected in HVNP that I did not find in this roadsides, ants show little penetration into study: Plagiolepis alluaudi, Technomyrmex nearby undisturbed forest. The ant species albipes (Smith), Camponotus variegatus (F. present in the park may have little ability to Smith), Hypoponera cf. sinensis, and Para invade intact montane forest. Alternatively, trechina vaga (Forel). All, except P. vaga, are ants may simply have not yet spread to suit "lowland" species that may be currently re able habitat in the forest. stricted to lower-elevation regions of HVNP. The two most recent surveys in Hawai'i Alternatively, it is possible that these species Volcanoes National Park (Jorgensen et al. do occur in the area surveyed in this study, [unpubl. data] and this study) found many but eluded collection because of their habits. more ant species than previous studies. Sev For example, P. alluaudi and T albipes tend eral of the previously uncollected ant species to be arboreal (David 1961, Wetterer 1997) are surprisingly widespread. For example, and C. variegatus is nocturnal (Reimer 1994). in this study, Cardiocondyla venustula, Car Hypoponera sinensis appears to be rare; Jor diocondyla nuda, and Tapinoma melanoce gensen et al. (unpubl. data) collected it only phalum occurred at 29, 10, and 9 sites, re once in HVNP. Whether this one specimen spectively. The two most recent ant surveys is-actually H-sinensis is--questionable- {to were- m0re -th()f0ugh than previous- studies, Morrison, pers. comm.). Additional arboreal, and this alone may explain the increase in the nocturnal, or rare ant species may also have number of species collected. There is strong been missed in my study, along with species evidence, however, that ants are spreading not attracted to tuna bait. Also, in some rapidly in the park. For example, neither Ants in Hawai'i Volcanoes National Park-WETTERER 47

Huddleston and Fluker (1968) nor Gagne Hawai'i (1770 m elevation [Wetterer et al. (1979) found A. longipes in HVNP, even in 1998]). Eight other ant species I collected in their low-elevation collections. Medeiros et the geothermal areas and building sites are al. (1986) collected A. longipes at three sites: also usually restricted to elevations below 900 at sea level, at 365 m elevation, and a single m (Table 1). individual worker under a garbage can at Anoplolepis longipes and Ph. megacephala Namakani Paio campground (1190 m eleva appear to have displaced most other ant spe tion). Currently in HVNP, both along the cies from the HQ geothermal area, but do coast and in the HQ geothermal area, A. not occur at the Puhimau hot spot. It appears longipes occurs at such remarkably high den that Ph. megacephala and A. longipes have sities that hundreds of ants covered the tuna not colonized this isolated habitat island. Al bait in a matter of minutes. In addition, the though the Puhimau hot spot is at a lower back porch of Volcano House is swarming elevation than the HQ geothermal area and with these ants. It seems unlikely that such closer to a possible source of colonization by populations were simply overlooked by the lowland ants, there is little human traffic to earlier studies. Rather, it seems more proba the Puhimau area. ble that A. longipes has invaded these areas Thermal habitat islands occur around within the past decade and is multiplying geothermal areas worldwide (e.g., see Glime rapidly. and Iwatsuki 1994). Often these areas are Haines et al. (1994) stated that the spread highly alkaline, enriched with sulfur and of A. longipes to new areas in the Seychelles other chemicals, and are inhabited only by "is almost certainly due to the accidental tolerant species. Geothermal vents, in such transfer of colonies in vehicles and in pro areas as Yellowstone National Park, USA, duce, such as coconut husks, vegetables, and are the sources of numerous unique ther building material." Similarly, Cole et al. mophilic microorganisms (Brock 1978, Pool (1992) believed that human activity was re 1990). The ecological significance of geother sponsible for the spread of L. humile in the mal habitat islands for native Hawaiian spe highlands of Maui. My observations of three cies in HVNP deserves further study. Geo introductions of ants into HVNP support the thermal areas may serve as refuges for less proposal that human activity is at least partly cold-tolerant native species, particularly in responsible for the spread of ants through the winter months. Some ofthese species may Hawai'i Volcanoes National Park. The ex in turn serve as food resources for other na press mail delivery of ants into the park is tive species. Whether any endemic Hawaiian particularly worrisome. Using this route, tem species are found only in geothermal areas is perate ant species may now bypass the unknown. tropical conditions of Honolulu and arrive of Hawai'i. directly in the highlands Possible Impact ofAnts in Hawai'i Volcanoes National Park Geothermal Areas and Buildings as "Habitat The spread of exotic ants through Hawai'i Islands" Volcanoes National Park poses a serious The geothermal areas and park buildings threat to endemic Hawaiian species. High appear to serve as "habitat islands" of densities of Ph. megacephala and A. longipes warmer climate that allow these ant species threaten endemic Hawaiian invertebrate and to extend their ranges to higher elevations. plant species found around high-elevation The K11auea Caldera region is the highest geothermal areas and nearby disturbed areas. _elevation recorded_for A. 10ngipes-inHawai'i In addition, these ant populations may serve (also see Medeiros et al. 1986). The only as a source for the spread of ants to other higher-elevation collection site in Hawai'i for high-elevation sites. The potential impact of Ph. megacephala is a single isolated collec Ph. megacephala and A. longipes at high ele tion site on the western slope of Mauna Kea, vations in Hawai'i, however, depends on the 48 PACIFIC SCIENCE, Volume 52, January 1998 ability of these ants to survive at high eleva phorid flies (Disney 1994), could be particu tions away from geothermal areas and build larly successful (Reimer et al. 1990). ings. Recent surveys have found Ph. mega cephala at high elevations on the saddle between Mauna Loa and Mauna Kea (Wet ACKNOWLEDGMENTS terer et al. 1998 and P. Oboyski, unpubl. data). The potential impact ofmore cold-tolerant I thank M. Wetterer, S. Shumway, N. ants may be even more profound. The great Reimer, S. Oboyski, L. Morrison, S. Miller, impact of L. humile on native fauna in drier C. Jorgensen, J. Glime, and D. Foote for highland regions of Hawai'i has been docu comments on the manuscript; P. Banko and mented, but the importance of L. humile in L. Laniawe for logistics and moral support; wetter highlands appears to be much more S. Cover for identifying the ants; all the limited. The rare occurrence and low density workers and volunteers at Hawai'i Volcanoes of H punctatissima supports Reimer's (1994) National Park for their friendship and kind conclusion that the ecological importance of ness; and C. Jorgensen for supplying un this species is "probably minimal." The eco published data on his collections of ants in logical importance of more common cold Hawai'i. tolerant ant species, such as P. bourbonica and C. venustula, remains unknown. Paratre china bourbonica has the potential for serious LITERATURE CITED impact in montane regions of Hawai'i Vol canoes National Park because it appears to BANKO, W. E., andP. C. BANKO. 1976. Role be able to colonize all habitats, including in of food depletion by foreign organisms in tact forest. A congener of this species, Para historical decline of Hawaiian forest birds. trechina fulva (Mayr), is an important pest Pages 29-34 in Proceedings of the 1st where it has been introduced (Zenner-Polania Conference on Natural Sciences, Hawai'i 1994). Cardiocondyla venustula is common at Volcanoes National Park. University of elevations up to 2000 m on nearby Mauna Hawai'i, Honolulu. Kea (unpubl. data). The highland forests of BOLTON, B. 1977. The ant tribe Tetramoriini Hawai'i Volcanoes National Park must be (Hymenoptera: Formicidae): The genus protected against human disturbance and the Tetramorium Mayr in the Oriental and introduction of additional ant species that Indo-Australian regions, and in Australia. may thrive in highland forests. Bull. Brit. Mus. Nat. Hist. Entomol. Decisions on future conservation of natu 36: 67-151. ral areas in Hawai'i may depend critically on ---. 1987. A review of the Solenopsis the current distribution ofpest ants as well as genus-group and revision of Afrotropical their potential future distributions. A data Monomorium Mayr (Hymenoptera: For base on the distribution of ants in the Ha micidae). Bull. Brit. Mus. Nat. Hist. waiian Islands should be useful, not only to Entomol. 54: 263-452. other researchers interested in examining the BROCK, T. D. 1978. Thermophilic micro impact of ants, but also to researchers exam organisms and life at high temperatures. ining other ecological questions where the Springer-Verlag, New York. presence or absence of ants should be con COLE, F. R., A. C. MEDEIROS, L. L. LOOPE, trolled. Establishing a baseline for the dis and W. W. ZUEHLKE. 1992. Effects of the tribution of pest ant species in Hawai'i is Argentine ant on arthropod fauna of Ha essential for any large-scale studies of ant waiian high-elevation shrubland. Ecology management ancleontF01~'I·he-dfectiveness-. .73: 1313-J322._ of control methods must be gauged against DAVID, A. L. 1961. Notes on the biology of known distributions. Because there are no the tree-ant Technomyrmex sp. near albipes native Hawaiian ants, biological control using Smith (Dolichoderinae: Formicoidea). J. ant-specific parasites, such as many species of Bombay Nat. Hist. Soc. 58: 289-293. Ants in Hawai'i Volcanoes National Park-WETTERER 49

DISNEY, R. H. L. 1994. Scuttle flies: The management. University of Hawai'i Press, Phoridae. Chapman and Hall, London. Honolulu. ELTON, C. S. 1958. The ecology of invasions HOWARTH, F. G., S. H. SOHMER, and W. D. by animals and plants. Methuen, London. DUCKWORTH. 1988. Hawaiian natural FELLERS, J. H., and G. M. FELLERS. 1982. history and conservation efforts. Bio Status and distribution of ants in the Science 38: 232-237. Crater District of Ha1eaka1a National HUDDLESTON, E. W., and S. S. FLUKER. 1968. Park. Pac. Sci. 36:427-437. Distribution of ant species of Hawaii. FLUKER, S. S., and J. BEARDSLEY. 1970. Proc. Hawaii. Entomol. Soc. 20: 45-69. Sympatric associations ofthree ants: Irido HUDDLESTON, E. W., A. A. LAPLANTE, and myrmex humilis, Pheidole megacephala, S. S. FLUKER. 1968. Pictorial key of the and Anoplolepis longipes in Hawaii. Ann. ants of Hawaii based on the worker Entomol. Soc. Am. 63: 1290-1296. forms. Proc. Hawaii. Entomol. Soc. 20: GAGNE, W. C. 1979. Canopy-associated 71-79. arthropods in Acacia koa and Metrosi MEDEIROS, A. c., L. L. LooPE, and F. R. deros tree communities along an altitudi COLE. 1986. Distribution of ants and their nal transect on Hawaii Island. Pac. Insects effects on endemic biota of Haleakala and 21: 56-82. Hawaii Volcanoes National Park: A pre GILLESPIE, R. G., and N. REIMER. 1993. The liminary assessment. Pages 39-52 in Pro effect of alien predatory ants (Hyme ceedings of the 6th Conference on Natural noptera: Formicidae) on Hawaiian en Sciences, Hawai'i Volcanoes National demic spiders (Araneae: Tetragnathidae). Park, Hawai'i. Pac. Sci. 47:21-33. NEWELL, W., and T. C. BARBER. 1913. The GLIME, J. M., and Z. IWATSUKI. 1994. Geo Argentine ant. U.S. Dep. Agric. Bur. thermal communities of Ponpnyama, Entomol. Bull. 122: 1-98. Hokkaido, Japan. J. Hattori Bot. Lab. ORIANS, G. H. 1986. Site characteristics 75: 133-147. favoring invasions. Pages 133-148 in HAINEs, 1. H., J. B. HAINEs, and J. M. H. A. Mooney and J. A. Drake, eds. CHERRETT. 1994. The impact and control Ecology of biological invasions of North of the crazy ant, Anoplolepis longipes America and Hawaii. Ecological Studies (Jerd.), in the Seychelles. Pages 206-218 in 58. Springer-Verlag, New York. D. F. Williams, ed. Exotic ants: Biology, POOL, R. 1990. Pushing the envelope of life. impact, and control of introduced species. Science (Washington, D.C.) 247: 158-160. Westview Press, Boulder, Colorado. REIMER, N. J. 1994. Distribution and impact HARDY, D. E. 1979. Report of preliminary of alien ants in vulnerable Hawaiian eco entomological survey of Pua'alu'u stream, systems. Pages 11-22 in D. F. Williams, Maui. Coop. Natl. Park Resour. Study ed. Exotic ants: Biology, impact, and con Unit, Univ. Hawaii Tech. Rep. 27: 34 trol of introduced species. Westview Press, 39. Boulder, Colorado. HOLLDOBLER, B., and E. O. WILSON. 1990. REIMER, N. J., J. W. BEARDSLEY, and G. The ants. Harvard University Press, JAHN. 1990. Pest ants in the Hawaiian Cambridge, Massachusetts. Islands. Pages 40-50 in R. K. Vander HOLWAY, D. A. 1995. Distribution of the Meer, K. Jaffe, and A. Cedeno, eds. Ap Argentine ant (Linepithema humile) in plied myrmecology, a world perspective. northern California. Conserv. BioI. 9: Westview Press, Boulder, Colorado. 1634-1637. SCOTT, J. M., S. MOUNTAINSPRING, F. L. HOWARTH, F. G. 1985. Impacts of alien land RAMSEY, and C. B. KEPLER. 1986. Forest arthropods and mollusks on native plants bird communities of the Hawaiian Islands: and animals in Hawai'i. Pages 149-179 in Their dynamics, ecology, and conserva C. P. Stone and J. M. Scott, eds. Hawai'i's tion. Stud. Avian BioI. 9: 1-431. terrestrial ecosystems: Preservation and SWANEY, D. 1994. Tonga. A lonely planet 50 PACIFIC SCIENCE, Volume 52, January 1998

travel survival kit. Lonely Planet Pub WILSON, E. 0., and R. W. TAYLOR. 1967. lications, Hawthorn, Australia. Ants of Polynesia. Pac. Insects Monogr. TRAGER, J. C. 1984. A revision of the genus 14: 1-109. Paratrechina (Hymenoptera: Formicidae) ZENNER-POLANIA, I. 1994. Impact of Para of the continental United States. Socio trechina fulva on other ant species. Pages biology 9:49-162. 121-132 in D. F. Williams, ed.. Exotic WETTERER, J. K. 1997. Ants on Cecropia in ants: Biology, impact, and control of Hawaii. Biotropica 29: 128-132. introduced species. Westview Press, Boul WETIERER, J. K., P. C. BANKo, L. LANlAWE, der, Colorado. J. W. SLOTTERBACK, and G. BRENNER. ZIMMERMAN, E. C. 1941. Argentine ant in 1998. Nonindigenous ants at high ele Hawaii. Proc. Hawaii. Entomol. Soc. vations on Mauna Kea, Hawai'i. Pac. Sci. 11: 108. 52 (in press). ---. 1948. Insects of Hawaii. Vol. 1. In WILSON, E. O. 1992. The diversity of life. W. troduction. University of Hawai'i Press, W. Norton and Company, New York. Honolulu.